This invention pertains to a radial-flow, horizontal-axis fluid turbine, also referred to herein as a rotary, fluid-flow-to-mechanical/electrical conversion device. More specifically, it relates to certain aerodynamic rotor features in such device which function to capture, efficiently, a relatively high percentage of mechanical energy resident in an oncoming fluid flow. For purposes of disclosure herein, a preferred and best mode embodiment of the invention is illustrated and described in the context of initially capturing wind(fluid)-flow energy for direct conversion to rotational-mechanical output power—a setting wherein the invention has been found to offer particular utility. The invention is additionally illustrated and described herein, in relation to this preferred embodiment, in the further useful context of converting such converted-to rotational-mechanical power to electrical output power. Thus, I use above, and elsewhere herein, the phrase “mechanical/electrical”. I intend this phrase to mean either one of two things in the context of this patent application. They are: (a) conversion of fluid-flow power directly to rotational-mechanical power; or (b) conversion of fluid-flow power (through a phase of rotational-mechanical power) to electrical output power.
For many years, and now discussing the present invention and its background in the “world” of providing electrical power, there has been an extensive effort, still enthusiastically underway, to develop high-efficiency, fluid-driven, rotary, electrical-output systems capable of the high-efficiency capturing (for ultimate conversion to electrical power) of mechanical power resident in a flow of fluid, such as in a flow of wind. For electrical power-output purposes, captured fluid-flow power is first usually converted to rotational-mechanical power, and then further converted to ultimately useful electrical power. As those skilled in the art will recognize, efforts to achieve higher and higher efficiencies in this context, as well as in the predecessor context of developing purely rotational-mechanical power from fluid flow, have traditionally centered on improving various aerodynamic qualities of wind(fluid)-responsive rotary devices.
As will be seen, the present invention offers certain significant contributions in relation to such efforts—contributions which are believed to be important and useful in different fluid-flow-related, mechanical-output/electrical-output environments.
In particular, the present invention focuses on a certain, special, rotor-related dimensional ratio, and on certain, special rotor airfoil (fluid-foil) configurations, each of which features has been discovered to lead to an advance in the efficiency of extracting mechanical power from, for example, wind for the purpose thereafter of enabling an efficient fluid-flow to rotational-mechanical conversion of energy, as well as an ultimate (if desired) rotational-mechanical-to-electrical conversion of energy. A preferred embodiment of the invention, which also reflects a best known mode of implementing the invention, is described and illustrated herein wherein a particular numerical, dimensional ratio, and a special cross-section-transitioning airfoil (fluid-foil) blade configuration, independently make individual as well, when optionally combined, as collective improvements to wind-power-extraction capability and efficiency.
The preferred embodiment of the illustrated invention takes the form generally of a cup-shaped, squirrel-cage, rotational-mechanical-energy-developing rotor possessing a perimetral distribution of plural, circumferentially spaced, elongate airfoil (fluid-foil) blades whose long axes substantially parallel the rotational axis of the rotor. The rotor, which is suitably coupled (in an “ultimate”, electrical-power-output setting which is specifically focused-upon herein for illustration purposes) to a rotary electrical generator (itself per se conventional), includes front and rear sides, with the front side being defined by a substantially planar, annular front ring occupying a plane which lies substantially normal to the rotor's rotational axis. The rotor's blades are, as just suggested, distributed circumferentially around this ring, and are attached to it with their long axes substantially normal to the plane of the ring. These blades extend rearwardly from the front ring toward the rear side of the rotor, which rear side is closed off by what is referred to herein as a back-plate structure. This back-plate structure, together with the portion of the rotor specifically including the airfoil blades, gives the rotor the mentioned cup-shaped configuration.
Each blade, as viewed transversely along its long axis, is arcuate in shape, and possesses, relative to that arcuate shape, a defined, transverse chord length which, along with blade-to-blade circumferential spacing, is another dimension that plays a role in the above-mentioned special dimensional ratio.
In one embodiment of the invention, each blade has substantially the same transverse cross-sectional configuration along its entire length. In another, alternative embodiment of the invention, the transverse curvature of each blade transitions from being (a) more arched near that end of the blade which is disposed adjacent the rear of the rotor, toward (b) a less arched configuration near the opposite end of the blade disposed adjacent the front of the rotor.
With respect to the special dimensional ratio mentioned above, this ratio is that of blade-to-blade circumferential spacing to blade transverse chord length.
Another feature of the invention, relative to a modified form thereof, includes the option of providing a forwardly facing nacelle located on the rotational axis of the rotor, with this nacelle being operable to provide a certain amount of horizontal-to-radial wind deflection with respect to oncoming wind.
To emphasize certain comments made above, it should be understood that the present invention may be structured and used both (a) purely for the conversion of fluid-flow power to rotational-mechanical power, as well as (b) for the additional conversion from rotational-mechanical power to electrical output power. For this reason, and as was suggested earlier, I use the phrase “mechanical/electrical” at certain location in the text of this application to emphasize this important point.
Other features and advantages that are offered by the present invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.
It should be understood that components, and associated spacings and dimensions, shown in these drawings are not presented necessarily to scale.